Apparatus and method for diagnosis and therapy of electrophysiological disease

ABSTRACT

The invention provides apparatus and methods for mapping conduction pathways and creating lesions in the heart wall for the treatment of atrial fibrillation. The apparatus may include at least one epicardial ablation probe having a plurality of electrodes for creating a lesion. The apparatus and method facilitate the formation of a lesion which electrically isolates the pulmonary veins from the surrounding myocardium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 09/440,825 filed Nov. 15,1999, now U.S. Pat. No. 6,474,340, which is a continuation of Ser. No.09/356,476 filed Jul. 19, 1999, now U.S. Pat. No. 6,311,692, which is acontinuation in part of Ser. No. 09/157,824 filed Sep. 21, 1998, nowU.S. Pat. No. 6,237,605.

FIELD OF THE INVENTION

This invention relates generally to the diagnosis and treatment ofelectrophysiological diseases of the heart, and more specifically todevices and methods for epicardial mapping and ablation for thetreatment of atrial fibrillation.

BACKGROUND OF THE INVENTION

Atrial fibrillation results from disorganized electrical activity in theheart muscle, or myocardium. The surgical maze procedure has beendeveloped for treating atrial fibrillation and involves the creation ofa series of surgical incisions through the atrial myocardium in apreselected pattern so as to create conductive corridors of viabletissue bounded by scar tissue. While very effective in treating atrialfibrillation, the maze procedure is highly invasive, high in moribidityand mortality, and difficult to perform by even the most skilledsurgeons. The procedure not only requires a median sternotomy or otherform of gross thoracotomy for access to the heart, but requires stoppingthe heart and establishing cardiopulmonary bypass, to which asignificant part of the trauma, morbidity and mortality of the mazeprocedure may be attributed.

As a less invasive alternative to the surgical incisions used in themaze procedure, transmural ablation of the heart wall has been proposed.Such ablation may be performed either from within the chambers of theheart (endocardial ablation) using endovascular devices (e.g. catheters)introduced through arteries or veins, or from outside the heart(epicardial ablation) using devices introduced into the chest throughsurgical incisions. Various ablation technologies have been proposed,including cryogenic, radiofrequency (RF), laser and microwave. Theablation devices are used to create elongated transmural lesions—thatis, lesions extending through a sufficient thickness of the myocardiumto block electrical conduction—which form the boundaries of theconductive corridors in the atrial myocardium. Perhaps most advantageousabout the use of transmural ablation rather than surgical incisions isthe ability to perform the procedure on the beating heart without theuse of cardiopulmonary bypass.

In performing the maze procedure and its variants, whether usingablation or surgical incisions, it is generally considered mostefficacious to include a transmural incision or lesion that isolates thepulmonary veins from the surrounding myocardium. The pulmonary veinsconnect the lungs to the left atrium of the heart, and join the leftatrial wall on the posterior side of the heart. This location createssignificant difficulties for endocardial ablation devices for severalreasons. First, while many of the other lesions created in the mazeprocedure can be created from within the right atrium, the pulmonaryvenous lesions must be created in the left atrium, requiring either aseparate arterial access point or a transeptal puncture from the rightatrium. Second, the elongated and flexible endovascular ablation devicesare difficult to manipulate into the complex geometries required forforming the pulmonary venous lesions and to maintain in such positionsagainst the wall of the beating heart. This is very time-consuming andcan result in lesions which do not completely encircle the pulmonaryveins or which contain gaps and discontinuities. Third, visualization ofendocardial anatomy and endovascular devices is often inadequate andknowing the precise position of such devices in the heart can bedifficult, resulting in misplaced lesions. Fourth, ablation within theblood inside the heart can create thrombus which, in the right chambers,is generally filtered out by the lungs rather than entering thebloodstream. However, on the left side of the heart where the pulmonaryvenous lesions are formed, thrombus can be carried by the bloodstreaminto the coronary arteries or the vessels of the head and neck,potentially resulting in myocardial infarction, stroke or otherneurologic sequelae. Finally, the heat generated by endocardial deviceswhich flows outward through the myocardium cannot be preciselycontrolled and can damage extracardiac tissues such as the pericardium,the phrenic nerve and other structures.

If, on the other hand, epicardial ablation devices are utilized to formthe pulmonary venous lesions, other challenges are presented. First, theposterior location of the pulmonary veins is extremely difficult toaccess through thoracic incisions without gross manipulations of theheart. Such manipulations are not generally possible ifminimally-invasive techniques are being utilized via small thoracicaccess ports, or if the procedure is being performed on a beating heartwithout cardiopulmonary bypass. Further complicating epicardial accessare the pericardial reflections, where the pericardium attaches to theheart wall near the pulmonary veins. The pericardial reflections arelocated so as to prohibit positioning a device completely around thepulmonary veins without cutting away or puncturing through thereflections. Such cutting or puncturing of the pericardial reflectionsis risky and difficult, particularly if working through small incisionsin the chest without a clear view and open access to the posterior sideof the heart. Furthermore, surgical repair of any damaged tissue isalmost impossible without highly invasive open heart surgery.

What are needed, therefore, are devices and methods for formingtransmural lesions that isolate the pulmonary veins from the surroundingmyocardium which overcome these problems. The devices and methods willpreferably be utilized epicardially to avoid the need for access intothe left chambers of the heart and to minimize the risk of producingthrombus. The devices and methods should be useful through small accessports in the chest using minimally invasive techniques. The devices andmethods will preferably avoid the need for cutting or puncturing thepericardial reflections, however, the pericardial reflections may be cutwithout departing from the scope of the invention. The devices andmethods should further be useful on the beating heart without requiringthe use of cardiopulmonary bypass and should not require significantmanipulation or retraction of the heart.

SUMMARY OF THE INVENTION

The present invention meets these and other objectives by providingepicardial ablation devices and methods useful for creating transmurallesions that electrically isolate the pulmonary veins for the treatmentof atrial fibrillation. The devices and methods may be utilized througha small access port in the chest, preferably through a subxiphoidpenetration, and positioned within the pericardium and around thepulmonary veins. Advantageously, the devices and methods do not requirethe large thoracic incision used in the conventional maze procedure, andmay be used on the beating heart without cardiopulmonary bypass. Byeliminating the need for ablation within the left atrium, the risk ofthrombus formation is minimized. The devices and methods of theinvention are more easily visualized, faster to use, and more accuratelypositionable than known cardiac ablation catheters and devices, enablethe formation of continuous, uninterrupted lesions around the pulmonaryveins, and protect extracardiac tissues from injury.

In a first embodiment, a method of forming a transmural lesion in a wallof the heart adjacent to the pulmonary veins comprises the steps ofplacing at least one ablation device through a thoracic incision andthrough a pericardial penetration so that the at least one ablationdevice is disposed in contact with an epicardial surface of the heartwall; positioning the at least one ablation device adjacent to thepulmonary veins on a posterior aspect of the heart while leaving thepericardial reflections intact; and transmurally ablating the heart wallwith the at least one ablating device to create at least one transmurallesion adjacent to the pulmonary veins. The ablation device ispreferably placed through a small puncture, incision, or access port inthe chest, either between the ribs or in a subxiphoid position, forminimal trauma, with visualization provided by fluoroscopy, endoscopy,transesophageal echocardiography, or other conventional form ofminimally-invasive imaging. While the method may be performed with theheart stopped and circulation supported with cardiopulmonary bypass, themethod is preferably performed with the heart beating so as to minimizemorbidity, mortality, complexity and cost.

In another aspect of the invention, an apparatus for forming atransmural lesion in the heart wall adjacent to the pulmonary veinscomprises, in a preferred embodiment, an elongated flexible shaft havinga working end and a control end; an ablation device attached to theworking end for creating a transmural lesion in the heart wall; acontrol mechanism at the control end for manipulating the working end;and a locating device near the working end configured to engage one ormore of the pulmonary veins, or a nearby anatomical structure such as apericardial reflection, for positioning the working end adjacent to thepulmonary veins. The locating device may comprise a catch, branch, notchor other structure at the working end configured to engage one or moreof the pulmonary veins or other anatomical structure such as theinferior vena cava, superior vena cava, aorta, pulmonary artery, leftatrial appendage, right atrial appendage, or one of the pericardialreflections. The ablation device may be a radiofrequency electrode,microwave transmitter, cryogenic element, laser, ultrasonic transduceror any of the other known types of ablation devices suitable for formingtransmural lesions. Preferably, the apparatus includes a plurality ofsuch ablation devices arranged along the working end in a linear patternsuitable for forming a continuous, uninterrupted lesion around or on thepulmonary veins.

The working end may additionally include one or more movable elementsthat are manipulated from the control end and which may be moved into adesired position after the working end has been located near thepulmonary veins. Slidable, rotatable, articulated, pivotable, bendable,pre-shaped or steerable elements may be used. Additional ablationdevices may be mounted to these movable elements to facilitate formationof transmural lesions. The movable elements may be deployed to positionsaround the pulmonary veins to create a continuous transmural lesionwhich electrically isolates the pulmonary veins from the surroundingmyocardium.

In addition, a mechanism may be provided for urging all or part of theworking end against the epicardium to ensure adequate contact with theablation devices. This mechanism may be, for example, one or moresuction holes in the working end through which suction may be applied todraw the working end against the epicardium, or an inflatable balloonmounted to the outer side of the working end such that, upon inflation,the balloon engages the inner wall of the pericardium and forces theworking end against the epicardium. This also functions to protectextracardiac tissues such as the pericardium from injury by retractingsuch tissues away from the epicardial region which is being ablated,and, in the case of the balloon, providing an insulated barrier betweenthe electrodes of the ablation probe and the extracardiac tissues.

The apparatus may be either a single integrated device or two or moredevices which work in tandem. In either case, the apparatus may have twoor more tips at the working end which are positioned on opposing sidesof a tissue layer such as a pericardial reflection. A device may beprovided for approximating the two free ends on opposing sides of thetissue layer, such as an electromagnet mounted to one or both of thefree ends. In this way, a continuous lesion may be created in themyocardium from one side of the pericardial reflection to the otherwithout puncturing or cutting away the pericardial reflection.

The apparatus may further include a working channel through whichsupplemental devices may be placed to facilitate visualization, tissuemanipulation, supplementary ablation, suction, irrigation and the like.

The apparatus and methods of the invention are further useful formapping conduction pathways in the heart (local electrograms) for thediagnosis of electrophysiological diseases. Any of the electrodes on theapparatus may be individually selected and the voltage may be monitoredto determine the location of conduction pathways. Alternatively, theapparatus of the invention may be used for pacing the heart bydelivering current through one or more selected electrodes at levelssufficient to stimulate heart contractions.

Additionally, although the ablation apparatus and methods of theinvention are preferably configured for epicardial use, the principlesof the invention are equally applicable to endocardial ablationcatheters and devices. For example, an endocardial ablation apparatusaccording to the invention would include a locating device configured toengage an anatomical structure accessible from within the chambers ofthe heart such as the coronary sinus (from the right atrium), pulmonaryartery (from the right ventricle), or the pulmonary veins (from the leftatrium), and the ablation device would be positionable in apredetermined location relative to the locating device. The endocardialapparatus could further include suction holes, expandable balloons, orother mechanisms for maintaining contact between the ablation device andthe interior surface of the heart wall.

In another aspect of the present invention, an anchor is used to hold apart of the device while displacing another part of the device. Theanchor is preferably a balloon but may also be tines, a suction port ora mechanically actuated device. After actuating the anchor, a proximalportion of the device may be moved by simply manipulating the device orby advancement or withdrawal of a stylet.

The present invention is also related to a method of creating acontinuous ablation lesion in tissue underlying a pericardial reflectionwithout penetrating the pericardial reflection. First and secondablating devices are introduced into the space between the pericardiumand the epicardium. The first ablating device is positioned on one sideof the pericardial reflection and the second ablating device ispositioned on the other side of the pericardial reflection. Tissuebeneath the pericardial reflection is then ablated with one or both ofthe devices to create a continuous lesion beneath the pericardialreflection. The devices may be aligned across the pericardial reflectionby any suitable method such as with magnetic force, use of an emitterand sensor, or by marking the pericardial reflection on one side andlocating the mark from the other side of the pericardial reflection. Theemitter and sensor may work with electromagnetic radiation such aslight, ultrasound, magnetic field, and radiation.

In yet another aspect of the invention, the ablating device may have aguide portion which aligns the device between the pericardium andepicardium. The guide portion may be a continuous strap or a number ofdiscrete guide portions. The guide portions may be fins, wings or one ormore laterally extending elements such as balloons. The guide portionsmay be individually actuated to align the device and ablate discretelocations of the tissue along the ablating device.

The ablating device may also be advanced into position over a guide. Theguide is preferably a guidewire but may be any other suitable structure.The guide may also lock into position with a coaxial cable or lockingarm. The guide is advanced ahead of the ablation device and positionedalong the desired ablation path. The ablating device is then advanced orretracted along the guide. The ablating device preferably includes adevice for locating previously formed lesions so that subsequent lesionswill merge with previously formed lesion to create a continuous,transmural lesion. The device for locating previously created lesionsmay be pacing and sensing electrodes or electrodes which simply measureelectrical impedance.

Although cutting through the pericardial reflections has certain risks,the methods and devices of the present invention may, of course, bepracticed while cutting through the pericardial reflections. Afterpenetrating through the pericardial reflection, the ablating device mayinterlock with another part of the same device or with a separatedevice.

Other aspects and advantages of the invention are disclosed in thefollowing detailed description and in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is side view of a left ablation probe according to theinvention.

FIG. 1B is a side view of a right ablation probe according to theinvention.

FIGS. 2A-2F are side views of a working end of the left ablation probeof FIG. 1A in various configurations thereof.

FIG. 3 is a side cross-section of the working end of the left ablationprobe of FIG. 1A.

FIG. 4 is a transverse cross-section of the shaft of the left ablationprobe of FIG. 1A.

FIGS. 5A-C are partial side cross-sections of the working end of theleft ablation probe of FIG. 1A, showing the deployment of a superiorsub-probe and inner probe thereof.

FIG. 6 is a side view of the left ablation probe of FIG. 1A.

FIG. 7 is a partial side cross-section of the handle of the leftablation probe of FIG. 1A.

FIG. 8 is an anterior view of the thorax of a patient illustrating thepositioning of the left and right ablation probes according to themethod of the invention.

FIG. 9 is a side view of the interior of a patient's thorax illustratingthe positioning of the left and right ablation probes according to themethod of the invention.

FIG. 10 is a posterior view of a patient's heart illustrating the use ofthe left and right ablation probes according to the method of theinvention.

FIG. 11 is a posterior view of a patient's heart illustrating atransmural lesion formed according to the method of the invention.

FIGS. 12 and 13 are side views of the left ablation probe of theinvention positioned on a patient's heart, showing a balloon and suctionports, respectively, on the inner probe.

FIG. 14 shows the ablating device having a pre-shaped distal portion.

FIG. 15 shows the ablating device having a flexible distal portion whichis shaped with a stylet.

FIG. 16 is a cross-sectional view of the ablating device of FIGS. 14 and15 with three chambers of the balloon inflated.

FIG. 17 is a cross-sectional view of the ablating device of FIGS. 14 and15 with two chambers of the balloon inflated.

FIG. 18 shows the ablating device advanced into the transversepericardial sinus with the balloon deflated.

FIG. 19 shows the ablating device advanced into the transversepericardial sinus with the balloon inflated.

FIG. 20 shows the ablating device extending between the left and rightinferior pulmonary veins and another ablating device having an endsuperior to the right superior pulmonary vein.

FIG. 21 shows the ablating device moved toward the right superior andright inferior pulmonary veins.

FIG. 22 shows one of the ablating devices having an emitter and theother ablating device having a sensor for aligning the devices across apericardial reflection.

FIG. 23 shows the ablating device having a needle to deliver a markerwhich is located on the other side of the pericardial reflection.

FIG. 24 shows the ablating device having a number of discrete guideportions.

FIG. 25 shows the guide portions being inflatable balloons.

FIG. 26 shows selective inflation of the balloons for selective ablationalong the ablating device.

FIG. 27A shows the guide portions used when ablating around thepulmonary veins.

FIG. 27B shows the guide portions being inflatable when ablating aroundthe pulmonary veins.

FIG. 28 is a bottom view of another ablating device which is advancedover a guide.

FIG. 29 is a top view of the ablating device of FIG. 28.

FIG. 30 is a cross-sectional view of the ablating device of FIGS. 28 and29 along line A—A of FIG. 29.

FIG. 31 is another cross-sectional view of the ablating device of FIGS.28 and 29 along line B—B of FIG. 29.

FIG. 32 shows the guide advanced to a desired location with the balloondeflated.

FIG. 33 shows the ablating device advanced over the guide and creating afirst lesion.

FIG. 34 shows the ablating device creating a second lesion continuouswith the first lesion.

FIG. 35 shows the ablating device creating a third lesion continuouswith the second lesion.

FIG. 36 shows another ablating device having an expandable devicemovable thereon.

FIG. 37 is a cross-sectional view of the ablating device of FIG. 36.

FIG. 38 is an enlarged view of the cross-sectional view of FIG. 37.

FIG. 39 shows the ablating device with a piercing element in a retractedposition.

FIG. 40 shows the ablating device aligned across the pericardialreflection.

FIG. 41 shows the ablating device interlocked with another ablatingdevice on opposite sides of the pericardial reflection.

FIG. 42 shows a mechanism for locking the first and second ablatingdevices together.

FIG. 43 shows the piercing element engaging a lock on the other ablatingdevice.

FIG. 44 shows the ablating device passing through the pericardialreflection and interlocking with itself.

FIG. 45 shows the ablating devices interlocked across the pericardialreflections.

FIG. 46 shows the ablating device adhered to a pericardial reflectionwith suction.

FIG. 47 shows the penetrating element penetrating the pericardialreflection.

FIG. 48 shows the ablating device passing through the pericardialreflection.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIGS. 1A-1B illustrate a first embodiment of the apparatus of theinvention. In this embodiment, the apparatus comprises a left ablationprobe 20, shown in FIG. 1A, and a right ablation probe 22, shown in FIG.1B, which work in tandem to form a transmural lesion isolating thepulmonary veins from the surrounding myocardium. Left ablation probe 20has a flexible shaft 21 extending to a working end 24 configured forinsertion into the chest cavity through a small incision, puncture oraccess port. Opposite working end 24, shaft 21 is attached to a controlend 26 used for manipulating the working end 24 from outside the chest.Shaft 21 is dimensioned to allow introduction through a small incisionin the chest, preferably in a subxiphoid location, and advanced to thepulmonary veins on the posterior side of the heart. Preferably, shaft 21is configured to be flexible about a first transverse axis to allowanterior-posterior bending and torsional flexibility, but relativelystiff about a second transverse axis perpendicular to the firsttransverse axis to provide lateral bending stiffness. In an exemplaryembodiment, shaft 21 has a length in the range of about 10-30 cm, and aguide portion 25 having a rectangular cross-section with awidth-to-height ratio of about 2-5, the cross-sectional width beingabout 6-35 mm and the cross-sectional height being about 3-17 mm. Theguide portion 25 aligns the device between the epicardium andpericardium to ablate tissues as described below. Shaft 21 is made of aflexible biocompatible polymer such as polyurethane or silicone, andpreferably includes radiopaque markers or a radiopaque filler such asbismuth or barium sulfate.

Working end 24 includes a plurality of ablating elements 27. Theablating elements 27 are preferably a plurality of electrodes 28 fordelivering radiofrequency (RF) current to the myocardium so as to createtransmural lesions of sufficient depth to block electrical conduction.Electrodes 28 may be partially-insulated solid metal rings or cylinders,foil strips, wire coils or other suitable construction for producingelongated lesions. Electrodes 28 are spaced apart a distance selected sothat the lesions created by adjacent electrodes contact or overlap oneanother, thereby creating a continuous, uninterrupted lesion in thetissue underlying the electrodes. In an exemplary embodiment, electrodes28 are about 2-20 mm in length and are spaced apart a range of 1-6 mm.It is understood that the term electrodes 28 as used herein may refer toany suitable ablating element 27. For example, as an alternative to RFelectrodes, the ablating elements 27 may be microwave transmitters,cryogenic element, laser, heated element, ultrasound, hot fluid or othertypes of ablation devices suitable for forming transmural lesions. Theheated element may be a self-regulating heater to prevent overheating.Electrodes 28 are positioned so as to facilitate lesion formation on thethree-dimensional topography of the left atrium. For example, lateralelectrodes 28 a face medially to permit ablation of the myocardium onthe lateral side of the left inferior pulmonary vein and medialelectrodes 28 b face anteriorly to permit ablation of the posteriorsurface of the myocardium adjacent to the left inferior pulmonary vein.

Working end 24 further includes a locating mechanism which locates theworking end at one of the pulmonary veins and helps to maintain it inposition once located. In a preferred embodiment, working end 24 isbifurcated into two branches 30, 32, and the locating mechanism is anotch 34 disposed between the two branches. Notch 34 tapers into aconcave surface 36 so as to receive one of the pulmonary veins betweenbranches 30, 32 and to atraumatically engage the pulmonary vein againstconcave surface 36. In an exemplary embodiment, notch 34 is about 10 to30 mm in width at its widest point between branches 30, 32 and taperstoward concave surface 36 which has a radius of curvature of about 4 to15 mm, so as to conform to the outer curvature of the pulmonary vein.Preferably, notch 34 is sized and positioned for placement against theleft inferior pulmonary vein, as described more fully below.Alternatively, the locating mechanism may be configured to engageanother anatomic structure such as the inferior vena cava, superior venacava, pericardial reflections, pulmonary vein, aorta, pulmonary artery,atrial appendage, or other structure in the space between thepericardium and the myocardium. The various shapes of the ablatingdevices described and shown herein are, of course, useful in locatingvarious structures to position the ablating elements againstpredetermined tissues to be ablated.

Working end 24 further includes a superior sub-probe 38 and an inferiorsub-probe 40 which are slidably extendable from working end 24, asfurther described below.

Control end 26 includes a handle 42 and a plurality of slidableactuators 44A-44E, which are used to extend superior sub-probe 38 andinferior sub-probe 40 from working end 24, and to perform otherfunctions as described below. An electrical connector 46 suitable forconnection to an RF generator is mounted to handle 42 and iselectrically coupled to electrodes 28 at working end 24. Also mounted tohandle 42 are a working port 48 in communication with a working channel92, described below, and a connector 50 for connection to a source ofinflation fluid or suction, used for purposes described below.

Right ablation probe 22 has a flexible shaft 52 extending from a controlend 54 to a working end 56. Working end 56 has a cross-member 58 towhich are mounted a plurality of electrodes 60. Cross member 58preferably has tips 59 which are pre-shaped or deflectable into a curveso as to conform to the right lateral walls of the right pulmonaryveins, and which are separated by a distance selected so that the tworight pulmonary veins may be positioned between them, usually a distanceof about 20-50 mm. Electrodes 60 are sized and positioned so as tocreate a continuous lesion along the right side (from the patient'sperspective) of the pulmonary veins as described more fully below. In anexemplary embodiment, electrodes 60 are about 2-20 mm in length, and arespaced apart about 1-6 mm. Shaft 52 is dimensioned to allow introductionthrough a small incision in the chest, preferably in a subxiphoidlocation, and advanced to the pulmonary veins on the posterior side ofthe heart. Shaft 52 will have dimensions, geometry and materials likethose of shaft 21 of left ablation probe 20, described above.

Control end 54 includes a handle 62. An electrical connector 64 adaptedfor connection to an RF generator is attached to handle 62 and iselectrically coupled to electrodes 60 at working end 56. An inflation orsuction connector 65 is mounted to handle 62 and adapted for connectionto a source of inflation fluid or suction, for purposed described below.Handle 62 may further include a working port (not shown) like workingport 48 described above in connection with left ablation probe 20.

FIGS. 2A-2E illustrate the deployment of the various components ofworking end 24 of left ablation probe 20. Superior sub-probe 38 isslidably extendable from working end 24 as shown in FIG. 2B. A pluralityof electrodes 66 are mounted to superior sub-probe 38 and are sized andpositioned to create a continuous lesion along the left side of thepulmonary veins. Superior sub-probe 38 has an articulated or steerablesection 68 which can be selectively shaped into the position shown inFIG. 2C, with its distal tip 70 pointing in a lateral direction relativeto the more straight proximal portion 72.

As shown in FIG. 2D, an inner probe 74 is slidably extendable fromsuperior sub-probe 38 and is directed by steerable section 68 in alateral direction opposite notch 34. Inner probe 74 is separated fromnotch 34 by a distance selected such that inner probe 74 may bepositioned along the superior side of the pulmonary veins when the leftinferior pulmonary vein is positioned in notch 34. In an exemplaryembodiment, the maximum distance from concave surface 36 to inner probe74 is about 20-50 mm. A plurality of electrodes 76 are mounted to innerprobe 74 and positioned to enable the creation of a continuoustransmural lesion along the superior side of the pulmonary veins asdescribed more fully below.

Referring to FIG. 2E, inferior sub-probe 40 is slidably extendable fromworking end 24. Its distal tip 78 is attached to a tether 80 extendingthrough a lumen in shaft 21. Tether 80 may be selectively tensioned todraw distal tip 78 away from inner probe 74 (toward control end 26),imparting a curvature to inferior sub-probe 40. Inferior sub-probe 40 isconstructed of a resilient, bendable plastic which is biased into astraight configuration. When inferior sub-probe 40 has been advancedsufficiently, tether 80 may be released, whereby the resiliency ofinferior sub-probe 40 causes it to conform to the pericardial reflectionand the medial and/or inferior sides of the four pulmonary veins.Inferior sub-probe 40 further includes a plurality of electrodes 82sized and positioned to produce a continuous transmural lesion in themyocardium along the inferior side of the pulmonary veins, as describedmore fully below.

Referring to FIGS. 3 and 4, superior sub-probe 38 is slidably disposedin a first lumen 84 and inferior sub-probe 40 is slidably disposed in asecond lumen 86 in shaft 21. Electrodes 28 along notch 34 are coupled towires 88 disposed in a wire channel 90 running beneath electrodes 28 andextending through shaft 21. Each electrode is coupled to a separate wireto allow any electrode or combination of electrodes to be selectivelyactivated. Shaft 21 also includes a working channel 92 extending to anopening 94 in working end 24 through which instruments such asendoscopes, suction/irrigation devices, mapping and ablation devices,tissue retraction devices, temperature probes and the like may beinserted. Superior sub-probe 38 has an inner lumen 96 in which innerprobe 74 is slidably disposed. Electrodes 76 on inner probe 74 arecoupled to wires 98 extending through inner probe 74 to connector 46 onhandle 42, shown in FIG. 1A. Similarly, electrodes 66 on superiorsub-probe 38 are coupled to wires 99 (FIG. 4) and electrodes 82 oninferior sub-probe 40 are coupled to wires 100, both sets of wiresextending to connector 46 on handle 42. Tether 80 slidably extendsthrough tether lumen 102 in shaft 21.

The distal end of inner probe 74 has a tip electrode 104 for extendingthe transmural lesion produced by electrodes 76. Preferably, inner probe74 further includes a device for approximating the tip of inner probe 74with the superior tip 106 of right ablation probe 22 (FIG. 1B) when thetwo are separated by a pericardial reflection. In a preferredembodiment, a first electromagnet 108 is mounted to the distal end ofinner probe 74 adjacent to tip electrode 104. First electromagnet 108 iscoupled to a wire 110 extending to handle 42, where it is coupled to apower source and a switch (not shown) via connector 46 or a separateconnector. Similarly, a second electromagnet 112 is mounted to distaltip 78 of inferior sub-probe 40, adjacent to a tip electrode 114, whichare coupled to wires 116, 118 extending to a connector on handle 42. Asshown in FIG. 1B, a third electromagnet 120 is mounted to superior tip106 of right ablation probe 22, and a fourth electromagnet 122 ismounted to inferior tip 124 of right ablation probe 22. Electromagnets120, 122 are coupled to wires (not shown) extending to a connector onhandle 62 for coupling to a power source and switch. In this way,superior tip 106 and inferior tip 124 may be approximated with innerprobe 74 and inferior sub-probe 40 across a pericardial reflection byactivating electromagnets 108, 112, 120, 122.

It should be noted that thermocouples, thermistors or other temperaturemonitoring devices may be mounted to the working ends of either left orright ablation probes 20, 22 to facilitate temperature measurement ofthe epicardium during ablation. The thermocouples may be mountedadjacent to any of the electrodes described above, or may be welded orbonded to the electrodes themselves. The thermocouples will be coupledto wires which extend through shafts 21, 52 alongside the electrodewires to connectors 46, 64 or to separate connectors on handles 42, 62,facilitating connection to a temperature monitoring device.

FIGS. 5A-5C illustrate the operation of superior sub-probe 38. Superiorsub-probe 38 has a pull wire 126 movably disposed in a wire channel 128in a sidewall adjacent to inner lumen 96. Pull wire 126 is fixed at itsdistal end 130 to steerable section 68 of superior sub-probe 38.Steerable section 68 is constructed of a flexible, resilient plasticsuch that by tensioning pull wire 126, steerable section 68 may bedeformed into a curved shape to direct inner probe 74 in a transversedirection relative to the straight proximal portion 72, as shown in FIG.5B. Once in this curved configuration, inner probe 74 may be slidablyadvanced from superior sub-probe 38 as shown in FIG. 5C.

Referring to FIG. 6, actuator 44D is slidably disposed in a longitudinalslot 132 in handle 42 and is coupled to the proximal end of inferiorsub-probe 40. Actuator 44E is slidably disposed in a longitudinal slot134 in handle 42 and is coupled to the proximal end of tether 80. Whensub-probe 40 is to be deployed, actuator 44D is slid forward, advancinginferior sub-probe 40 distally. Actuator 44E may be allowed to slideforward as well, or it may be held in position to maintain tension ontether 80, thereby bending sub-probe 40 into the curved shape shown inFIG. 2E. When sub-probe 40 has been fully advanced, actuator 44E may bereleased, allowing distal end 78 of sub-probe 40 to engage thepericardial reflection along the inferior surfaces of the pulmonaryveins, as further described below.

Actuators 44A-C are slidably disposed in a longitudinal slot 136 inhandle 42, as more clearly shown in FIG. 7. Actuator 44A is attached tothe proximal end of superior sub-probe 38, and may be advanced forwardto deploy the sub-probe from working end 24, as shown in FIG. 2A.Actuator 44B is attached to inner probe 74, which is frictionallyretained in inner lumen 96 such that it is drawn forward with superiorsub-probe 38. Actuator 44C is attached to pull wire 126 which is alsodrawn forward with superior sub-probe 38. In order to deflect thesteerable section 68 of superior sub-probe 38, actuator 44C is drawnproximally, tensioning pull wire 126 and bending steerable section 68into the configuration of FIG. 2C. Finally, to deploy inner probe 74,actuator 44B is pushed forward relative to actuators 44A and 44C,advancing inner probe 74 from superior sub-probe 38 as shown in FIG. 2D.

The slidable relationship between the shafts and probes 74, 40, 38 helpsto guide and direct the probes to the tissues to be ablated. The shaftshave various features, including the ablating elements 27, however, theshafts may be simple sheaths which locate structures and/or direct theprobes into various regions of the pericardial space.

Referring now to FIGS. 8-11, a preferred embodiment of the method of theinvention will be described. Initially, left ablation probe 20 and rightablation probe 22 are connected to an RF generator 140. RF generator 140will preferably provide up to 150 watts of power at about 500 kHz, andwill have capability for both temperature monitoring and impedancemonitoring. A suitable generator would be, for example, a Model No.EPT-1000 available from the EP Technologies Division of BostonScientific Corp, of Natick, Mass. Retraction, visualization, temperaturemonitoring, suction, irrigation, mapping or ablation devices may beinserted through working port 142. Left ablation probe 20 may further beconnected to a source of suction or inflation fluid 144, for reasonsdescribed below. If electromagnets are provided on left and rightablation probes 20, 22 as described above, an additional connection maybe made to a power supply and switch for operating the electromagnets,or power may be supplied by RF generator 140 through connectors 46, 64.

A subxiphoid incision (inferior to the xiphoid process of the sternum)is made about 2-5 cm in length. Under direct vision through suchincision or by visualization with an endoscope, a second small incisionis made in the pericardium P (FIG. 9). Left ablation probe 20 isintroduced through these two incisions and advanced around the inferiorwall of the heart H to its posterior side under fluoroscopic guidanceusing fluoroscope 146. Alternative methods of visualization includeechocardiography, endoscopy, transillumination, and magnetic resonanceimaging. Left ablation probe 20 is positioned such that left inferiorpulmonary vein LI is disposed in notch 34 as shown in the posterior viewof the heart in FIG. 10.

Superior sub-probe 38 is then advanced distally from working end 24until its steerable section 68 is beyond the superior side of the leftsuperior pulmonary vein LS. Steerable section 68 is then deflected intothe curved configuration shown in FIG. 10 such that its distal end 70 issuperior to the left superior pulmonary vein LS and pointing rightwardtoward the right superior pulmonary vein RS. Inner probe 74 is thenadvanced toward the right until its distal tip is very close to orcontacting the pericardial reflection PR superior to the right superiorpulmonary vein RS.

Inferior sub-probe 40 is next advanced from working end 24 whilemaintaining tension on tether 80 such that the inferior sub-probeengages and conforms to the shape of the pericardial reflection PRbetween the left inferior and right inferior pulmonary veins. Wheninferior sub-probe 40 has been fully advanced, tension is released ontether 80 so that distal tip 78 moves superiorly into engagement withthe right inferior pulmonary vein RI adjacent to pericardial reflectionPR inferior thereto.

Right ablation probe 22 is placed through the subxiphoid incision andpericardial incision and advanced around the right side of the heart asshown in FIG. 8. Under fluoroscopic guidance, right ablation probe 22 ispositioned such that cross-member 58 engages the right superior andinferior pulmonary veins, as shown in FIG. 10. In this position,superior tip 106 and inferior tip 124 should be generally in oppositionto distal tip 75 of inner probe 74 and distal tip 78 of inferiorsub-probe 40, respectively, separated by pericardial reflections PR. Inorder to ensure close approximation of the two tip pairs, electromagnets108, 120, 114, 122 may be energized, thereby attracting the tips to eachother across the pericardial reflections RS.

It should be noted that the pericardium P attaches to the heart at thepericardial reflections PR shown in FIGS. 10-11. Because of theposterior location of the pulmonary veins and the limited access andvisualization available, cutting or puncturing the pericardialreflections in the vicinity of the pulmonary veins poses a risk ofserious injury to the heart or pulmonary veins themselves. The apparatusand method of the present invention avoid this risk by allowing thepericardial reflections to remain intact, without any cutting orpuncturing thereof, although the pericardial reflections may also be cutwithout departing from the scope of the invention.

RF generator 140 is then activated to deliver RF energy to electrodes28, 60, 66, 76, 82, 104, and 112 on left and right ablation probes 20,22, producing the transmural lesion L shown in FIG. 11. Preferably,power in the range of 20-150 watts is delivered at a frequency of about500 kHz for a duration of about 30-180 seconds, resulting in localizedmyocardial temperatures in the range of 45-95

C. Ultrasound visualization may be used to detect the length, locationand/or depth of the lesion created. Lesion L forms a continuouselectrically-insulated boundary encircling the pulmonary veins therebyelectrically isolating the pulmonary veins from the myocardium outsideof lesion L.

Ablation probes 20, 22 may further be used for mapping conductionpathways in the heart (local electrocardiograms) for the diagnosis ofelectrophysiological abnormalities. This is accomplished by selectingany of the electrodes on the ablation probes and monitoring the voltage.A commercially available electrophysiology monitoring system isutilized, which can select any electrode on the ablation probes andmonitor the voltage. Various electrodes and various locations on theheart wall may be selected to develop a map of potential conductionpathways in the heart wall. If ablation treatment is then required, thesteps outlined above may be performed to create transmural lesions atthe desired epicardial locations.

During any of the preceding steps, devices may be placed through workingport 142 and working channel 92 to assist and supplement the procedure.For example, a flexible endoscope may be introduced for visualization toassist positioning. Ultrasound probes may be introduced to enhancevisualization and for measuring the location and/or depth of transmurallesions. Suction or irrigation devices may be introduced to clear thefield and remove fluid and debris. Tissue manipulation and retractiondevices may be introduced to move and hold tissue out of the way.Cardiac mapping and ablation devices may also be introduced to identifyconduction pathways and to supplement the ablation performed by left andright ablation probes 20, 22.

Furthermore, mapping and ablation catheters, temperature monitoringcatheters, and other endovascular devices may be used in conjunctionwith the left and right ablation probes of the invention by introducingsuch devices into the right atrium or left atrium either through thearterial system or through the venous system via the right atrium and atranseptal puncture. For example, an ablation catheter may be introducedinto the left atrium to ablate any region of the myocardium notsufficiently ablated by left and right ablation probes 20, 22 in orderto ensure complete isolation of the pulmonary veins. Additionally,ablation catheters may be introduced into the right chambers of theheart, or epicardial ablation devices may be introduced throughincisions in the chest, to create other transmural lesions.

In some cases, it may be desirable to actively ensure adequate contactbetween the epicardium and the electrodes of left and right ablationprobes 20, 22. For this purpose, left ablation probe 20 and/or rightablation probe 22 may include one or more expandable devices such asballoons which are inflated in the space between the heart and thepericardium to urge the ablation probe against the epicardial surface.An exemplary embodiment is shown in FIG. 12, in which a balloon 150 ismounted to the outer surface of inner probe 74 opposite electrodes 76 onleft ablation probe 20. Inner probe 74 further includes an inflationlumen 152 in communication with an opening 154 within balloon 150 andextending proximally to inflation fitting 50 on handle 42, through whichan inflation fluid such as liquid saline or gaseous carbon-dioxide maybe delivered. When inflated, balloon 150 engages the inner surface ofthe pericardium P and urges inner probe 74 against the epicardialsurface of heart H. This ensures close contact between electrodes 76 andthe epicardium, and protects extracardiac tissue such as the pericardiumand phrenic nerve from injury caused by the ablation probes. Balloons orother expandable devices may similarly be mounted to superior sub-probe38, inferior sub-probe 40, or right ablation probe 22 to ensuresufficient contact between the epicardium and the electrodes on thosecomponents.

Alternatively or additionally, suction ports may be provided in theablation probes of the invention to draw the electrodes against theepicardium, as shown in FIG. 13. In an exemplary embodiment, suctionports 156 are disposed in inner probe 74 between or adjacent toelectrodes 76. Suction ports 156 are in communication with a suctionlumen 158 which extends proximally to suction fitting 48 on handle 42.In this way, when suction is applied through suction port 156, innerprobe 74 is drawn tightly against the heart, ensuring good contactbetween electrodes 76 and the epicardium. In a similar manner, superiorsub-probe 38, inferior sub-probe 40 and right ablation probe 22 mayinclude suction ports adjacent to the electrodes on those components toenhance contact with the epicardium.

Referring to FIGS. 14-17, the ablating device 20 is shown with variousfeatures described above. The embodiments of FIGS. 14-17 arespecifically referred to as ablating device 20A and like or similarreference numbers refer to like or similar structure. The ablatingdevice 20A may have any of the features of the ablating devices 20, 22described above and all discussion of the ablating devices 20, 22 or anyother ablating device described herein is incorporated here. Asmentioned above, the ablating device 20A may have a pre-shaped portion160 or a flexible or bendable portion 162 as shown in FIGS. 14 and 15,respectively. A stylet 164 or sheath (not shown) is used to shape theablating device 20A as described below. The stylet 164 passes through aworking channel 166 which may receive other devices as described above.The working channel 166 may also be coupled to a source of fluid 169,such as fluoroscopic contrast, which may be used for visualization. Thecontrast may be any suitable contrast including barium, iodine or evenair. The fluoroscopic contrast may be introduced into the pericardialspace to visualize structures in the pericardial space.

Referring to FIG. 14, the pre-shaped portion 160 has a curved or L-shapein an unbiased position. The distal portion of the device 20A may haveany other shape such as a hook or C-shape to pass the device 20A arounda structure. The stylet 164 holds the pre-shaped portion 160 in anyother suitable geometry, such as dotted-line 167, for introduction andadvancement of the ablating device 20A. The stylet 164 may also bemalleable. When the ablating device 20A is at the appropriate position,the stylet 164 is withdrawn thereby allowing the distal end 160 toregain the angled or curved shape. The device 20A may also be shapedwith a sheath (not shown) through which the device 20A passes in amanner similar to the manner of FIGS. 2 and 5.

Referring to FIG. 15, the ablating device 20A has the flexible distalportion 162 which is shaped by the stylet 164 into the dotted line 168position. The pre-shaped portion 160 may be used to position or advancethe ablating device 20A between the epicardium and pericardium. FIG. 18shows the pre-shaped portion positioned around the left superiorpulmonary vein as described below. A number of different stylets 164 maybe used to shape the flexible portion 162 around various structures.

The ablating device 20A also has an anchor 170 to anchor a portion ofthe device 20A while moving another part of the device 20A. When theanchor 170 is the balloon 150, the balloon may have a number of chambers171, preferably three, which can be inflated as necessary to positionthe device as shown in FIGS. 16 and 17. The chambers 171 are coupled toa source of inflation fluid 173 via inflation lumens 175. The anchor 170is preferably an expandable element 172 such as the balloon 150, but mayalso be tines which grab the epicardium, pericardium or pericardialreflection. The anchor 170 may also be one or more suction ports 156, asdescribed above (see FIG. 13). The suction ports 156 may be used toanchor the device to the pericardium, epicardium, pericardial reflectionor any other structure in the space between the pericardium andepicardium. Although only one anchor 170 is located at the distal end,the anchor 170 may be positioned at any other location and more than oneanchor 170 may be provided without departing from the scope of theinvention.

Referring to FIGS. 18-21, a specific use of the ablating device 20A isnow described. The ablating devices described herein may, of course, beused to ablate other tissues when positioned in the space between theepicardium and pericardium. The ablating device 20A is preferablyintroduced in the same manner as the ablating device 20 or in any othersuitable manner. When the ablating device 20A is at the entrance to thetransverse pericardial sinus, the ablating device 20A may be given theangled or curved shape by advancing or withdrawing the stylet 164 (seeFIGS. 14 and 15) or with the sheath (see FIGS. 2 and 5). The device 20Ais then advanced until the tip meets the pericardial reflection at theend of the sinus as shown in FIG. 18. The anchor 170, such as theballoon 150, is then actuated to resist movement of the distal end whendisplacing other parts of the ablating device 20A (FIG. 19). At thistime, the ablating device 20A may be used to ablate tissue in the mannerdescribed above from a position superior to the right superior pulmonaryvein, around the left superior pulmonary vein and to the left inferiorpulmonary vein. Thus, the ablating device 20A is similar to the ablatingdevice 20 described above in that the device 20A extends through thetransverse pericardial sinus and to the left inferior pulmonary vein.

The ablating device 20A, like the ablating device 20, may also have aportion 176 which is moved to ablate tissue inferior to the left andright inferior pulmonary veins. Stated another way, the portion 176 ismoved to a position inferior to the inferior pulmonary veins. Theportion 176 is moved into the position shown in FIG. 20 by simplypushing the device 20A to displace the portion 176 or by advancing orwithdrawing the stylet 164. After the ablating device 20A is properlypositioned, the ablating elements 27 are activated as described above tocreate transmural lesions.

Still referring to FIG. 20, another ablating device 22A may also be usedto ablate tissue in the same manner as the ablating device 22 describedabove. The ablating device 22A is introduced in the manner describedabove and is advanced until distal end 177 is positioned at a desiredlocation. FIG. 20 shows the distal end 177 superior to the rightsuperior pulmonary vein adjacent the pericardial reflection. A portion179 of the ablating device 20A is then moved to the position of FIG. 21in any manner described above such as by introduction or withdrawal ofthe stylet 164. The ablating device 20A is then used to ablate tissue asdescribed above.

The ablating device 20A, 22A are also similar to the ablating devices20, 22 in that the ablating devices 20A, 22A create continuous lesionson both sides of the pericardial reflections extending between the venacava and the right superior and right inferior pulmonary veins. Tissuebeneath the pericardial reflections is ablated using at least one of theablating devices 20A, 22A. The ablating devices 20A, 22A may beapproximated using any suitable technique or device such as withmagnetic force described above. Other methods and devices for creating acontinuous lesion beneath a pericardial reflection are described below.

Referring now to FIG. 22, another system and method for approximatingthe ablating devices 20, 22 and 20A, 22A is now described. An energyemitter 180, such as a light source 182, emits energy from the ablatingdevice 20A which is received by a sensor 184 on the other ablatingdevice 22A to determine when the devices 20A, 22A are positioned onopposite sides of a pericardial reflection. The emitter 180 and sensor184 preferably pass through the working channel 166 but may also beintegrated into the devices 20A, 22A. When the ablating devices 20A, 22Aare aligned across the pericardial reflection, the sensor 184 detectsproper alignment so that the lesion may be formed continuously on bothsides of the pericardial reflection.

Yet another method to make sure that the ablating devices 20A, 22A arealigned across a pericardial reflection is to mark a location on thepericardial reflection where a lesion has been created as shown in FIG.23. The device 20A has a needle 185 introduced through the workingchannel 166. The needle 185 delivers a marker 186, such as a radioopaquedye, which can be visualized. The device 20A may also deliver a solidmarker such as a platinum wire. An advantage of using the marker 186 isthat both ablating devices 20A, 22A do not need to be positioned onopposite sides of the pericardial reflection at the same time. Thus,only one ablating device 20A may be necessary to create a continuouslesion beneath the pericardial reflection since the same device 20A canmark the pericardial reflection on one side, locate the mark 186 on theother side, and continue the lesion on the other side of the pericardialreflection.

Referring again to FIG. 10, the ablating device 20 has the guide portion25. As mentioned above, the guide portion 25 preferably has a width toheight ratio of about 2 to 5. The guide portion 25 aligns the ablatingelement 27 against a predetermined structure, such as the pulmonaryveins, to ablate tissue. The relatively flat configuration of the guideportion 25 aligns the device 20 between the epicardium and thepericardium so that the ablating elements 27 are directed toward themyocardium.

Referring now to FIG. 24, an ablating device 20B is shown which has anumber of discrete guide portions 25A. Four guide portions 25A are shownin FIG. 24 with each guide portion 25A being shaped similar to a fin 29.The ablating device 20A may also have a beaded or scalloped appearance.The ablating device 20A preferably has flexible sections 188 between theguide portions 25A which provide torsional flexibility so that the guideportions 25A can rotate relative to one another. The guide portions 25Amay be positioned between the pulmonary veins as shown in FIG. 27A. Theablating device 20B may have any of the features of the other ablatingdevices 20, 20A described herein.

Referring to FIG. 25, another ablating device 20C is shown which hasguide portions 25B which may also be deployed after the ablating device20C has been positioned so that the guide portion 25B does not interferewith advancement and placement. The guide portion 25B has one or moreexpanding elements 192, such as the balloons 150, which may be expandedduring advancement or after the device 20A is at the desired location.The expanding elements 192 are positioned on opposite sides of theablating device 20C, however, the expanding elements 192 may bepositioned only on one side of the device 20C. The guide portions 25Amay be positioned between the pulmonary veins as shown in FIG. 27B. Theexpanding elements 192 may also be mechanically actuated elements suchas bending arms or an expandable mesh.

The expanding elements 192 may also be inflated at selected locations 10corresponding to discrete ablation sites as shown in FIG. 26. Anadvantage of individual expansion of the expanding elements 192 is thatother portions of the device 20C may rotate and displace as necessary toprovide good contact at the desired ablation site 193.

Another ablating device 20D is now described with reference to FIGS.28-31. The ablating device 20D is advanced over a guide 200 which isadvanced ahead of the device 199. The guide 200 is preferably aguidewire 202 having the anchor 170 to anchor an end 204 of the guide200. The guide 200 is advanced and positioned along the intendedablation path. The ablating device 20D is then retracted or advancedalong the guide 200 to create a continuous lesion along the intendedablation path. The guide 200 may also be locked into a desiredorientation with a coaxial cable or with a mechanism similar to lockingarms used to hold surgical devices. The ablating device 20D has anexpanding device 201, such as the balloon 150, to move the ablatingelement 27 into contact with the tissue to be ablated. The balloon 150preferably has a number of chambers 203, preferably at least two,coupled to inflation lumens 205, 207 which are coupled to the source ofinflation fluid 173 (FIG. 14). Electrodes 191, 193 are coupled to wires209, 211 passing through the device 20D. The guide 200 passes throughthe working channel 166. Wires 213 are also provided to steer, rotateand position the device 20D.

The ablating device 20D and/or the guide 200 preferably includes adevice 206 for aligning the ablating element with a previously createdlesion. The aligning device 206 may be electrodes 191, 193 which simplymeasure electrical impedance. When the electrodes 191, 193 measure alarge increase in electrical impedance an ablation is positioned beneaththe electrodes 191, 193. In this manner, the ablating element 27 can bealigned and positioned to create a continuous lesion through the tissue.Referring to FIG. 29, the electrodes 191, 193 may also be used to locatethe previously created lesion 195 as shown in FIG. 29. The electrode 191will sense a higher amplitude of activity than the electrode 193 sincethe electrode is positioned over the previously created lesion while theelectrode 191 is not.

Still referring to FIG. 28, the ablating device 20D may have first andsecond electrodes 194, 196 on opposite sides of the ablating element 27.The first electrode 194 may be a pacing electrode 195 which emits anelectrical impulse and the second electrode 196 may be a sensingelectrode 197 which receives electrical impulses. When the firstelectrode 194 emits a stimulus, launching a cardiac impulse, the impulseis transmitted through tissue to the sensing electrode 197 if adiscontinuity exists in the lesion. A number of sensing electrodes 197may be positioned along the ablating device 20A which may be used todetermine the location of a discontinuity. Both electrodes 194, 196 mayalso be sensing electrodes 197 with both electrodes 194, 196 merelysensing normal activity. When only one of the electrodes 194, 196 sensesthe activity an effective, continuous transmural lesion has beencreated. The electrodes described herein may be coupled to any suitabledevice including an ECG with electrogram amplitudes being measured.

The electrodes 194, 196 may also be used to locate the end of apreviously created lesion. The time between emission of the pacingstimulus to receipt of the cardiac impulse at the sensing electrodeincreases when a transmural ablation has been created between theelectrodes 194, 196. When such an increase is detected, it is known thatthe previously created lesion is positioned between the electrodes 194,196. The time between emission and receipt of the cardiac impulse mayalso be used in simple time of flight analysis to determine the locationof a discontinuity in the ablation. For example, the electrodes 194, 196are positioned at a discontinuity in an ablation when the time of flightis lowest.

A method of using the device is shown in FIGS. 32-35. The guide 200 isadvanced to a desired location and the anchor 170 is actuated. Theablating device 20D is then advanced over the guide 200, the balloon 150is inflated, and a first ablation 215 is performed. The balloon 150 isthen deflated and the ablating device 20C is then moved to anotherlocation. The electrodes 191, 193 or 194, 196, or other suitablealigning device, is used to position and align the ablating device 20Dand a second ablation 217 is then performed which is continuous with thefirst ablation 215. The device 20D is then moved again and a thirdablation 219 is formed continuous with the second ablation 217.

Referring to FIGS. 36-38, another ablating device 210 is shown whereinthe same or similar reference numbers refer to the same or similarstructure. The ablating device 210 has an expandable structure 209,preferably a balloon 150A, movable along the ablating device 210 toselectively anchor and align the device 210. An advantage of the systemof FIGS. 36-38 is that the structure 209 can be moved to variouslocations on the ablating device 210 for moving various ablatingelements into contact with tissue to be ablated. The ablating device 210also has the anchor 170, such as the balloon 150B, to anchor a part ofthe ablating device 210 and to move the ablating elements 27 intocontact with the tissue to be ablated. The balloon 150B is coupled to asource of inflation fluid 211 via inflation lumen 223.

The expandable device 209 is mounted to a body 211 having a scallopedappearance to provide flexibility although any other suitable design maybe used. The body 211 has a C-shaped cross-section which engages aflange 221 on the ablating device 210. The expandable device 209 ispreferably the balloon 150A but may be a mechanically actuated device.For example, the expandable device 209 can be an extendable arm, a wireloop or an expandable mesh. The anchor 170 may be selectively expandableto guide, rotate, and move the ablating device 210 as necessary. Theballoon 150A preferably has at least two separately inflatable chambers212 and FIG. 38 shows the balloon 150A having three independentlyinflatable chambers 212. The chambers 212 are coupled to inflationlumens 219 which are coupled to a source of inflation fluid 213. Thechambers 212 may be inflated as necessary to move and rotate theablating device 210 and press the ablating element 27 against the tissueto be ablated. The expandable structure 209 is moved to variouspositions along the ablating device 210 to move various ablatingelements 27 into contact with the tissue. The body 211 may also havepull wires 218 for further manipulation of the ablating device 210.

As mentioned above, penetrating the pericardial reflections carriesinherent risks. However, the methods and devices of the invention may,of course, be used when penetrating the pericardial reflections. Theablating devices 20, 22, 20A, 22A may have a penetrating element 220 asshown in FIGS. 39-43 for penetrating the pericardial reflections. Thepenetrating element 220 is movable from a retracted position (FIG. 40)to an extended position (FIG. 41). The penetrating element 220 passesthrough the working channel 166 of the ablating device 20A. Thepenetrating element 220 is preferably positioned in the working channel166 but may also be integrated into the ablating device 20A or may be aseparate device altogether. The first and second ablating devices 20A,22A are positioned on opposite sides of the pericardial reflection asshown in FIG. 40 using the emitter and sensor arrangement describedabove in connection with FIG. 22 although any other devices ortechniques may be used. The penetrating element 220 is then used topenetrate the pericardial reflection and the two devices 20A, 22A areinterlocked as shown in FIG. 41.

Referring to FIGS. 42 and 43, the ablating device 22A has a lockingmechanism 224 which holds the penetrating element 220. The lockingmechanism 224 has a stationary jaw 230 and a movable jaw 231. Themovable jaw 231 is movable in the direction of arrow 223 for releasingthe device 20A. The locking mechanism 224 is also positioned in theworking channel 166 of the ablating device 22A but may be integral withthe device 22A. The penetrating element 220 preferably has a conical tip222 or other cutting element for piercing the pericardial reflection butmay also be a laser, ultrasonic dissector, or electrosurgical device.The penetrating element 220 may also be a blade, needle or otherstructure for cutting or piercing the pericardial reflection. Afterablating tissue, the locking mechanism 224 is released, the penetratingelement 220 is retracted and the ablating devices 20A, 22A are removed.The ablating devices 20A, 22A may have any other interlockingconfiguration and the ablating device 22A may interlock with some otherstructure other than the penetrating element 220. Referring to FIG. 48,the ablating devices 20, 22 may interlock with one another in the mannerdescribed above. Referring to FIG. 44, the ablating device 20 maypenetrate through one or more pericardial reflections and interlock withanother part of the ablating device 20. Referring to FIG. 45, theablating device 20 and the ablating device 22 may also interlock acrossthe pericardial reflections using the penetrating element 220 or othersuitable device.

Referring to FIGS. 46-49, another method of penetrating and advancingthrough the pericardial reflection is shown. The end of the ablatingdevice 20A may be adhered to the pericardial reflection using suctionthrough the working channel 166. The penetrating element 220 is thenadvanced through the working channel 166 while suction is maintained sothat the piercing element is guided directly to the pericardialreflection. The penetrating element 220 is then used to penetrate thepericardial reflection as shown in FIG. 45. The ablating device 20A isthen advanced through the pericardial reflection as shown in FIG. 46.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, substitutions and modificationsmay be made without departing from the scope thereof, which is definedby the following claims. For example, any of the ablating devicesdescribed herein may have the anchor, fins, lateral balloons, sensors,and/or electrodes without departing from the scope of the invention.

1. A method of forming a lesion from a location in the pericardialspace, comprising the steps of: introducing a first ablating device intothe pericardial space, the ablating device having an ablating element;advancing the first ablating device to a pericardial reflection;penetrating the pericardial reflection with the first ablating device;and forming a first lesion with the ablating element.
 2. The method ofclaim 1, further comprising the step of: interlocking a first part ofthe first ablating device with a second part of the first ablatingdevice after the penetrating step.
 3. The method of claim 1, furthercomprising the steps of: introducing a second ablating device into thepericardial space; and interlocking the first and second ablatingdevices after the penetrating step.